Effect of the distal remnant on ileal adaptation

Abstract

The ileum has a greater adaptive capacity than the jejunum after intestinal resection, which may be, in part, related to increased exposure to luminal contents and intrinsic properties of the ileum. However, the intestinal remnant might contribute to this adaptive response as well. Our aim was to determine the effect of the distal intestinal remnant on ileal adaptation when the ileum is proximal in the intestinal tract. Twenty-one Lewis rats were included in the study. One group (n = 7) served as unoperated control subjects, the second group (n = 7) underwent transposition of the jejunum and ileum, and the third group (n = 7) underwent 50% proximal resection with syngeneic transplantation of the ileum. Nutritional status and structural adaptation were studied at 14 days. Animals in both the transposition and transplant groups initially lost weight but weights returned to above preoperative levels at 14 days. Food intake, stool weight, and serum albumin levels were similar in these two groups. Intestinal weight and diameter were similar in the proximal end of the ileal segment in the two study groups and were significantly increased compared to control values (0.26 ± 0.04 and 0.31 ± 0.02 vs. 0.10 ± 0.0 g/cm and 8.4 ± 0.5 and 9.1 ± 0.8 vs. 4.9 ± 0.3 mm; P <0.05). Intestinal weight and diameter of the distal end of the ileal segment were greater than those values in unoperated control animals but were greatest in the ileal transplant group (0.15 ± 0.1 and 0.24 ± 0.03 vs. 0.07 ± 0.01 g/cm and 5.6 ± 1.1 and 8.7 ± 0.6 vs. 4.3 ± 0.2 mm; P <0.05). Villus height and crypt depth were similar in both the proximal and distal ends of the ileal segments in the two study groups and were significantly increased compared to control values (642 ± 75 and 720 ± 15 vs. 411 ± 24 proximal and 443 ± 49 and 500 ± 46 vs. 343 ± 22 μm distal, P <0.05; 223 ± 34 and 244 ± 33 vs. 173 ± 20 proximal and 192 ± 28 and 209 ± 18 vs. 144 ± 26 μm distal, P <0.05). Proximal placement of the ileum by either transposition or transplantation results in structural adaptation. This occurs to a similar extent whether the distal remnant is jejunum or ileum. Thus increased exposure to luminal contents and intrinsic properties appear to be the important factors in the adaptive capability of the ileum when the ileum is the proximal portion of the intestinal tract.